A polishing composition including silica particles has been known as a polishing composition used to polish a silicon wafer that is used in the manufacture of a semiconductor substrate. In this type of polishing composition, there are problems such that the surface defects (LPD: light point defects) of a silicon wafer occur due to the agglomeration of the silica particles, and when the polishing composition is filtered to remove an agglomerate, the filter is clogged (see, e.g., Patent Document 1 and Patent Document 2). Moreover, in order to improve the polishing rate, a polishing composition that includes a water-soluble macromolecular compound including a nitrogen-containing group has been known (see Patent Document 3).